1. Field of the Invention
The present invention relates generally to electronic devices, and more particularly to systems and methods for sensing the temperature of devices such as integrated circuits.
2. Related Art
Integrated circuits such as microprocessors are becoming increasingly complex. The circuit components (e.g., transistors, diodes, resistors and the like) that form these devices are, at the same time, becoming increasingly small so that more and more functions may be performed by a particular integrated circuit. As the number of circuit components and functions grows, the amount of power that is typically consumed by these integrated circuits typically also increases. With the increased power consumption of the circuits, the amount of heat generated within the circuits increases as well. This heat may affect the performance of the devices, and may even cause the devices to fail.
As a result of the dangers presented by the generation of increased amounts of heat in electronic devices, it is often necessary to be able to detect temperatures within these devices. Thermal sensing circuits are therefore incorporated into some devices in order to detect dangerously high temperatures or even measure temperatures within the devices. For example, a thermal sensing circuit can be incorporated into an integrated circuit in order to sense the temperature of the circuit and determine whether the temperature exceeds a predetermined threshold. If the temperature exceeds this threshold, corrective action (e.g., reducing the activity within the circuit or even shutting down the circuit) can be taken in order to reduce the temperature to a safer level.
One way to implement a thermal sensing circuit is to provide a device or circuit that is sensitive to changes in temperature, and to compare a voltage generated by this device to a reference voltage. For example, a diode may be used for this purpose. When the voltage of the thermally sensitive device/circuit is equal to the reference voltage, the temperature is equal to a known temperature corresponding to this voltage. If the voltage of the thermally sensitive device/circuit is less (or greater) than the reference voltage, the temperature is lower (or higher) than the known temperature.
The relationship of temperature and voltage in the thermally sensitive device/circuit is typically well known, but in order to accurately determine the temperature of the device/circuit, it is necessary to know the voltage of the device/circuit with accuracy. The reference voltage is used for this purpose. The greater the accuracy with which the reference voltage is known, the greater the accuracy with which the temperature can be determined.
Conventionally, thermal sensing circuits are designed using a constant temperature-independent reference voltage. Typically, Bandgap reference circuit is used for this purpose, and a great deal of care is taken to ensure that the source of this reference voltage is very stable and insensitive to manufacturing variations, variations in temperature, etc. As a result, the source of the reference voltage is typically a complex circuit that includes a relatively large number of components and occupies a relatively large area on the chip in which it is implemented. It would be desirable to be able to provide systems and methods for thermal sensing that are less complex, and that require less area on the chip.